allgonebellyup...I think you are very naive.
My ex was alovely fella, we were together ten years, we went to uni together, we bought a house together, had two lovely kids together, he was a fantastic father and great to me.
There was no inkling at all about what he was going to do. Out of the blue he decided he'd had enough and ran off with a 16 year old schoolgirl. He was 27 and so was I.
Almost overnight he turned into an arrogant shite, who refused to pay for his kids, stopped paying the mortgage, leaving me to struggle on and work part time He eventually forced me to sell the house, leaving me and the kids homeless.
He went from seeing the kids everyday when we split up, then every weekend, then got kicked out of his mums, shacked up with his bitch and then decided his relationship was too important and rarely saw the kids and certainly didn't pay for them
Aren't you wonderfully lucky to habe an ex that sees his kids so regularly blah blah. You are a new single parent, just wait until your ex has a new relationship or another child by that person. Hopefully he will still be a good dad but you just never know.
Please don't judge.